Oil burner control



Jan. 1, 1935. c, HALL 1,985,986

OIL BURNER CONTROL- Filed Feb. 24. 1930 Inventor" Chester 1'. Hal l b5His Attorney Patented I, 1935 UNITED. STATES OIL BURNER CONTROLChester 1. Hall, Philadelphia, Pa asaignol' to General Electric Company,a corporation of New York Application February 24, 1930, Serial No.430,497

38 Claims.

My invention relates to control devices and has for its principal objecta fully automatic control device for aburner for fluids such as oil andgases, although it may be adapted to other burners which depend forignition upon an electric spark or hot filament, gas or oil flame andthe like.-

In oil burners making use of such ignition the spray of oil is notalways at first ignited. If the motor operating the oil pump continuesto function, after a failure to establish a flame, since no means areprovided to dissipate the oil enough oil may collect in the fire box tocause an explosion when ignition does take place.

Difliculty has also been experienced during operation due to slugs ofwater in the oil temporarily shutting off the oil supply and thusextinguishing the flame. Due to only a slight cooling of therefractories when the oil spray is againresumed, enough oil is permittedto accumulatev before ignition takes place to cause an explosion.

It is an object of the present'invention to automatically start the fuelsupply motor and the ignition system of the burner whenever there is acall for heat and to automatically shut down the apparatus when nofurther heat is needed.

Another object of my invention is to cut out the ignition system when aflame has been established and to lock in the fuel supply motor.

Another object of my invention is to provide means whereby severalopportunities are given the ignition device to ignite the oil, and ifthe flame still fails the apparatus will be made inoperative. To make itoperative it will be neces-- sary to reset the apparatus by hand, thuscalling for an inspection.

A further object of my invention is to prevent the accumulation of oilin a hot fire box and causing an explosion whenever the flame has beenextinguished.

Another object of my invention is to provide a safety device operativeto disconnect the whole apparatus whenever dangerous heat or pressureconditions arise.

A further object of my invention is the provision of an automatic meansfor changing the operating temperatures of the apparatus for day andnight operation. Other objects will hereinafter appear.

The preferred embodiment of my invention consists of a synchronous motorfor continuously driving a time controlled mechanism, whichautomatically switches in the nightor day thermostats which in turninitiate operation of the apparatus.

This motor also drives what is termed a recycling mechanism for openingand closing an ignition circuit at short intervals, thus presentingseveral opportunities for igniting the oil. When the flame isestablished a flame responsive device placed in the fire box of thefurnace and operated by the flame cuts out the ignition system and locksin the fuel supply motor.

The fuel supply motor is also controlled by the recycling device, themotor being operated at intervals simultaneously with the ignitionsystem. The intervals of operation are so spaced that any gases in thefire box are permitted to be drawn off by natural draft while the motorand ignition system are deenergized. Of course the ignition system couldbe continuously energized during recycling until a flame is established.

Should the flame fail during operation the flame responsive deviceenergizes the recycling mechanism to reignite the oil by reenergizingthe ignition system. A definite time period is provided after flamefailure before the ignition and fuel supply motor circuits arereestablished by the recycling device. This permits accumulated gasesopportunity to be drawn off.

The recycling operation is accomplished by means of cam actuatedcontacts which are rendered operative whenever a starting coil isenergized by the closing of a thermostat calling for heat. The startingcoil operates a pivoted member upon which a cam is mounted. This bringsthe cam shaft into contact with a driving pulley of the synchronousmotor. The rotation of the cam actuates the contacts to open and closethe ignition system and fuel supply motor circuits. In the event thatthe recycling device fails to cause ignition of the 011 after apredetermined number of intermittent operations of the fuel supply motorand ignition system, limiting or counting means are provided forrendering the recycling device inoperative, thus inviting inspection todetermine the cause of the failure less of the position of the timeswitch 12.

power supplied through lines L1 and In. This synchronous motor drives atime controlled switch 12 which makes contact with contact elements 13and 14. This motor also drives a pinion 15 which engages under certainconditions with the gear 16 mounted on the movable shaft 16 to drive therecycling cam 17. As shown one end of the shaft 16 is provided with apivot bearing and the other end is rotatably supported on the pivotedarmature 19 of the electromagnet 19. Thus when the electromagnet 19 isenergized to attract its armature 19', the shaft 16 is tilted so as tobring the gear 16 into driving relation with the pinion 15 and therebyrotate the recycling cam 17. Gear 16 is so designed that pinion 15 isprevented since the pinion- 15 will merely slip with respect to the gear16. This action takes place when the member supporting the lower contactof the pair of contacts 20 is in the last depression in the cm 1'7. Thusthe contacts will remain in the open position until the apparatus isinspected. The coiled spring 18, after electromagnet 19 has beendeenergized and the shaft 16' moved to disengage the gear 16 from pinion15, rotates the shaft 16' in a clockwise direction so that uponreenergization of the electromagnet 19 to effect tilting movement of theshaft 16' in the manner just described, the gear 16 will againengage-the pinion 15 to be driven thereby. 21 designates the ignitiontransformer which supplies the 11 energy to produce a spark at theelectrodes 22 for igniting the spray of oil. 23 is the fuel supplymotor. 24 and 24 designate mercury switches actuated by means of a stackthermostat 30.

31 designates a starting transformer and 32 a locking transformer whichis actuated by means of the electromagneticalLv operated member 33. 35and 36 designate the night and day thermostats and 3'7 designates aswitch for arbitrarily determining the controlling thermostat rege'lrlleoperation of this embodiment is as follows:

When the switch 50 is closed the primary of transformer 31 is energized.If the time control switch 12 is in contact with the element 13 and thethermostat 36 moves to the left hand contact in calling for heat, acircuit is completed through the secondary of the transformer 31,conductor 40, thermostat 36, switch 37, conductor 43, through the timeswitch, the electromagnetic device 33 and conductor 41 to the other sideof the transformer. This actuates device 33 closing its contacts andplacing the primary of transformer 32 across the line. A circuit iscompleted through the secondary of this transformer by means of itswinding. This looks transformer 32 into the circuit and prevents themovement of the thermostat 36 to a neutral position from disturbing theoperation of the device.

A safety switch 51 normally closed establishes a circuit from one sideof the line L: to one side of the ignition transformer 21 and one sideof the fuel supply motor 23. A circuit is established through theelectromagnetically operated device 19, contacts 28 and 29 of themercury switch 24' and the contacts of the electromagnetically operateddevice 33 to the opposite side of the line L1. 19 actuates its armatureto establish a driving connection between pinion 15 and gear 16 and uponrotation of the cam 17 in a counterclockwise direction the contacts 20are intermittently closed and opened. This closing of the contactsplaces the primary of transformer 21 across lines L1 and L2. Thiscircuit may be traced from line L: through switch 51 to one side of theprimary of the transformer 21, through the contact 20, contacts 28 and29 of mercury switch 24, through the contacts of the electromagneticallyoperated device 33 to the other side of the line L1. The circuit throughthe motor is also established from the line L2 through the switch 51,motor 23, contacts 25 and 26 of mercury switch 24, contacts 20, contacts29, 28 of mercury switch 24' and contacts of the device 33 to the otherside of the line L1.

Upon the establishment of a flame the stack thermostat 30 operates totilt the mercury switches 24 and 24', breaking the contacts at 26 and 29and establishing contact at 27 and 28 of switch 24'. The circuit throughdevice 19 is opened permitting the pinion and gears 15 and 16 to demesh.The cam is returned to its inoperative position. This action results intaking out of the circuit the primary of the ignition transformer 21 andin placing the motor 23 directly across lines L1 and L2 through contacts27, 28 of mercury switch 24' which circuit is maintained until thethermostat 36 is actuated to call for less heat.

When the thermostat 36 is caused by the room temperature to move to theright hand contact, the electromagnetically operated device 33 isshorted, thus deenergizing its coil and permitting the contacts to beopened. This opens the circuit through the motor and extinguishes theoil flame. Upon cooling of the gases in the stack the thermostat 30returns the mercury switches to their starting position to again renderthe recycling device operative to reestablish a flame when more heat iscalled for by the thermostat. As has been pointed out above, if no flameis established the recycling device will operate to lock contacts 20 inthe open position after a predetermined number of intermittentoperations of the recycling device. Under these conditions theelectromagnet 19 remains energized to hold the gear 16 in engagementwith the pinion 15 although there is no further rotation of the gear 16by the pinion 15 since the pinion merely slips with respect to the gear16 when it encounters the segmental. cutaway portion of the gear 16referred to above. When upon inspection the difliculty responsible forthe non-establishment of flame is corrected, it is then necessary toreset the control apparatus by hand to render it again operative toestablish flame. This manual resetting operation is accomplished bymomentarily opening the switch 51 and then reclosing this switch. Uponthe opening of switch 51, the electromagnet 19 is deenergized therebypermitting the coil spring 18 to return the gear 16 and the recyclingcam 17 to their initial position in the manner described above.

Thermostat 35 is rendered operative when the time switch 12 is incontact with segment 14 through conductor 42 and switch 37. A switch 37is provided which places either thermostat 35 or 36 in the controllingcircuit regardless of the position of the time switch, as will bereadily menses seen'by tracing out the circuits. Thus assuming contact12 of the time switch in engagement with the segment 13 and the switch37 in the position shown, thermostat 36 is included in the controllingcircuit.

switch 37 is rotated slightly in a counterclockwise direction. Assumingcontact 12 in engagement with the segment 14, thermostat 35 is in thecontrolling circuit with switch 37 in the position shown. However, aslight rotation of switch 37 in the clockwise direction will serve tocut out thermostat 35 and cut in thermostat 36. In other words, with theswitch 37 rotated from the position in which it is shown, slightly inthe counterclockwise direction, the thermostat 35 is effective tocontrol the heating apparatus with the contact 12 of the time switchengaging either of the segments 13 or 14. Conversely-with the switch 37rotated slightly in the clockwise direction, thermostat 36 controls theheating apparatus at all times.

The embodiment of the invention illustrated and described herein hasbeen selected for the purpose of clearly setting forth the purpose involved. It will be apparent however, that the invention is susceptibleof being modified to meet the different conditions encountered in itsuse and I therefore aim to cover by the appended claims allmodifications within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is- 1. In a heat control device, a normally continuouslyenergized operating electric motor, a circuit maker and breaker adaptedto be operated by said electric motor, a day and a night thermostatindividually operative for controlling operation of saidcircuit makerand breaker by said electric motor in accordance-with temperatureconditions, and a timer continuously operated by said electric motor forrendering the day and the night thermostat operative at predeterminedtime intervals.

2. In a heat control means, a fuel supply motor, an ignition systemtherefor, a plurality of thermostats, a recycling device including anelectric driving means, an adjustable time control switch fordetermining day and night operation of said thermostats and driven bysaid driving means, a circuit making and breaking means driven by saiddriving means for intermittently energizing the fuel supply motor andignition system under the control of said thermostats.

3. In a control device, an electric time control means, a circuit makingand breaking device, anelectro-responsive device to operate said circuitmaking and breaking device, a plurality of heat responsive devicesadapted to separate 1y control said electro-responsive device andconnections between said time controlled means and heat responsivedevices to determine selective operation of said heat responsive devicesat different' periods.

4. In a control device, an adjustable time control switch, an electricdriving motor therefor, a circuit making and breaking means adapted tobe interconnected with the motor for operation thereby,electro-responsive means for controlling the interconnection of thecircuit making and breaking means with the motor, a plu rality of heatresponsive devices for separately controlling the operation of saidelectro-responsive means, and connections between said time switch andheat-responsive devices'for selective- Then in case it is desiredtoplace the thermostat 35in the controlling circuit,

ly determining the separate operation of said heat responsive devices.

5. In a heat control system, a plurality of heat responsive means, atime control means for periodically determining individual operation ofsaid heat responsive means, and a member for determining operation ofsaid heat responsive means at any time and rendering said timecontrolled means ineffective.

6. In a heat control system, a night thermostat and a day thermostat, anadjustable time control switch for periodically determining theoperative thermostat, and a switching means for rendering said timecontrolled means inefiective and determining the operative thermostat atany time.

7. In an oil burner control system, a continuously operating electricmotor, an adjustable time control switch operated thereby, a fuel supplymotor and an electrical system for igniting the fuel, a cam operatedintermittent circuit mak ing and breaking device adapted'to be driven bysaid continuously operating motor and interconnected with said timeswitch for intermittently energizing said supply motor and ignitionsystem, a day thermostat and a night thermostat selectively renderedoperative by said time switch and electroresponsive means operatingunder the control of said thermostat to control the cam operated deviceto be driven by the motor and means operative upon establishing a flamefor deenergizing the ignition system and maintaining said fuel supplymotor energized.

8-. In an oil burner control system, a continuously operating electricmotor, a fuel supply motor and an ignition system for igniting the fuel,

for causing operation of said cam operated de-' vice by saidcontinuously operated motor, and means for deenergizing the ignitionsystem and maintaining said motor in operation uponestablishing a flame,and means rendering the said cam operated device inoperative uponfailure to establish a flame after a predetermined number ofintermittent operations.

9. In an oil burner control system, a fuel supply motor and anelectrical ignition system for igniting the fuel, a cam operated circuitmaking and breaking device for intermittently energizing said fuelsupply motor and ignition system to establish combustion, acontinuouslyoperating electric motor for'driving said cam operatedcircuit making and breaking device and normally disconnected therefrom,electroresponsive means for establishing operative connectionsbetweenthe continuously operating motor and the cam operated circuit making andbreaking device, a day and a night thermostatic switch for controllingsaid electroresponsive means, an adjustable time switch driven by saidcontinuously operated motor for selectively rendering the day and nightthermostatic switch operative to control said electroresponsive means,combustion responsive means for controlling said electroresponsive meansto disconnect said cam operated device from the continuously operating.motor, means controlled by said combustion responsive means formaintaining said fuel supply motor energized upon establishment ofcombustion and means rendering the cam operated device inactive uponfailure to establish combustion after a predetermined number ofintermittent operations.

10. In a heat control device, electrically operated heat control means,a normally continuously energized electric motor, switch mechanism forcontrolling the operation of said heat control means, a cam forintermittently operating said switch mechanism and adapted to be drivenby said motor, a member supporting said cam and movable from oneposition to another position to establish driving connections betweensaid motor and said cam, and thermostatic means for controlling thedriving connections between the motor and cam responsively topredetermined temperature conditions.

11. A mechanical relay in a heat control device, comprising a normallycontinuously energized electric motor, a cam shaft, a cam on said camshaft, means for supporting said cam shaft and movable from one positionto another position to establish driving connections between said motorand said cam shaft, a circuit maker and breaker adapted to beintermittently operated by said cam when said driving connections areestablished, and a heat responsive means for controlling movement ofsaid cam shaft supporting means to establish said driving connections inaccordance with temperature conditions.

12. A mechanical relay in a heat control device, comprising a normallycontinuously energized electric motor, heat control means including acircuit maker and breaker, a cam adapted to be driven by said motor forintermittently operating said circuit maker and breaker, a cam shaft forsupporting said cam and means for supporting said cam shaft and movablefrom one position to another position to establish driving connectionsbetween said motor and said cam shaft, and a thermostatic means forcontrolling movement of said cam shaft supporting means to establish thedriving connections between said motor and said cam shaft responsive topredetermined temperature conditions.

13. In a, heat control means, means for feeding fuel, means for ignitingsaid fuel, means for controlling said fuel-feeding means and saidigniting means for initiating combustion, means including a timing motorfor operating said controlling means intermittently until combustionoccurs, and means operated by said timing motor for limiting the numberof said intermittent operations to a predetermined number and fordisabling said controlling means when combustion fails to take placeafter said, predetermined number of intermittent operations.

14. A heating device including electrically operated means for feedingfuel, an electrically operated igniter therefor, circuits for energizingsaid fuel-feeding means and said igniter, control means for saidcircuits having a rotatable timing cam for causing intermittentenergization of said fuel-feeding means and said igniter to initiatecombustion, a second circuit for said fuelfeeding means, meansresponsive to combustion conditions for operating said timing cam toopen said first circuits, wherebyzsaid igniter is maintaineddeenergized, and for closing said second circuit to maintain saidfuel-supply motor energized when combustion is established, and atemperature-responsive device movable between two positions and movableto one position under predetermined temperature conditions for control-=ling operation of said intermittent control means to initiate combustionand movable to another position under other predetermined temperatureconditions for controlling said second circuit to deenergize saidfuel-supply motor.

15. A heating device including electrically operated means for feedingfuel, an electrically operated igniter therefor, controlling means forintermittently energizing said fuel-feeding means and said igniter toinitiate combustion, electromagnetic means for controlling operation ofsaid intermittent controlling means, a second electromagnetic meansforcontrolling energization of said first electro-magnetic means,temperature-responsive means responsive to predetermined temperatureconditions for energizing said second electro-magnetic means, acombustion-responive device for deenergizing said first electro-magneticmeans to cause deenergization of said igniter and for maintaining saidfuel-supply motor energized, said temperature-responsive meansdeenergizing said second electro-magnetic means under otherpredetermined temperature conditions for deenergizing said fuel-supplymeans.

16. In a heating apparatus, means for feeding fuel, means for ignitingthe fuel, means for controlling said fuel-feeding means and saidigniting means for initiating combustion, means for operating saidcontrolling means intermittently, a counting mechanism associated withsaid intermittent operating means to be advanced from an initialposition to a final position for limiting said intermittent operationsto a predetermined number, and means responsive to combustion conditionsfor rendering said intermittent means ineffective, for maintaining saidfuel feeding meansin operation and for resetting said counting mechanismto initial position when combustion is established 'before said countingmechanism reaches the final position.

17. In a heating apparatus, means for feeding fuel, means for ignitingsaid fuel, means for controlling said fuel-feeding means and saidigniting means for initiating combustion, timing means for operatingsaid controlling means intermittently until combustion occurs, acounting meansoperated by said timingmeans andmovable from an initialposition to a final position for limiting said intermittent operationsto a predetermined numher, and combustion-responsive means for renderingsaid counting means ineffective, for maintaining said fuel feeding meansin operation. and having electro-magnetic means associated therewith forcausing resetting of said counting means to initial position whencombustion is established.

18. In a heating apparatus, means for feeding fuel, means for ignitingsaid fuel, means for controlling said fuel-feeding means and saidigniting means for initiating combustion, timing means for operatingsaid controlling means intermittently, means operated by said timingmeans and movable from an initial position to a final positionfox-,limiting said intermittent operations to a predetermined number,electro-magnetic means operatively associated with said timing means andlimiting means to control the same, and combustion-responsive means forcontrolling said electro-magnetlc means to render said timing meansineffective to operate said controlling means, for maintaining said fuelfeeding means in operation, and for causing resetting of said limitingmeans to initial position when combustion is established.

19. In a heating apparatus, means for feeding fuel, ignition meanstherefor, a starting circuit for said fuel-feeding means, means forintermittently energizing said starting circuit. electromagnetic meansassociated with said intermittent means for controlling operation ofsaid intermittent means, a second electro-magnetlc means associated withsaid first electro-magnetic means to control energization of saidstarting circuit by said intermittent means, means associated with saidintermittent controlling means to be advanced from initial position to afinal position for limiting said intermittent operations to apredetermined number, a running circuit for said fuel-feeding means,means responsive to combustion for causing said first electro-magneticmeans to render said intermittent means ineffective, saidcombustion-responsive means cooperating with said secondelectro-magnetic means to close said running circuit upon establishingcombustion, said first electro-magnetic means causing resetting of saidlimiting means upon operation of said combustion-responsive means whencombustion is established.

20. In a control for a combustion heating device, the combination ofthermostatic control means, atiming motor having cooperatingelectromagnetic. means controlled by said thermostatic means forintermittently establishing combustion conditions for the heating deviceand means jointly controlled by said timing motor and saidelectromagnetic means for limiting the intermittent establishment ofcombustion conditions to a predetermined number.

21. In a combustion heating device, the com bination, of electricallyoperated fuel supply means, an electric igniter for the fuel, a timingmotor having electromagnetic circuit controlling means cooperatingtherewith for intermittently energizing said fuel supply means and saidigniter to establish combustion conditions, thermostatic means forcontrolling said electromagnetic means, and counting means jointlycontrolled by said timing motor and said electromagnetic means forlimiting the intermittent energizations of said fuel supply means andsaid igniter to a predetermined number.

22. In a fuel burner, the combination of a fuel supply motor, anelectric igniter, switchmechanism for controlling said fuel supplyinotor and igniter to initiate combustion, means including a constantspeed motor driven timing device for intermittently operating saidswitch mechanism, and counting means operated by said timing device forrendering said switch mechanism ineffective after a predetermined numberof intermittent operations.

. 23. In a combustion heating device, the combination of motor operatedfuel supply means, electric ignition means therefor, switch mechanismfor energizing said motor operated fuel supply means and said ignitionmeans to initiate combustion, a motor driven rotary cam timing devicehaving electromagnetic controlling means cooperating therewith forintermittently effecting operation of said switch mechanism, countingmeans operated by said timing device for rendering said switch mechanismineffective after a predetermined number of intermittent operations,means responsive to combustion cooperating with said electromagneticmeans for maintaining the motor operated fuel supply means continuouslyenergized upon establishment of combustion, and temperature responsivemeans for controlling said electromagnetic means to initiate andterminate operation of said fuel supply means.

' 24. In a combustion heating device, the combination of a fuel supplymotor, an electric igniter,

circuit controlling means including an electric motor driven rotary camtiming device having electromagnetic controlling means forintermittently energizing the fuel supply motor and igniter to establishcombustion, thermostatic means for controlling said circuit controllingmeans, counting means operated by said timing device from an initialposition to a final position for limiting the intermittent energizationsof said fuel supply motor and igniter to a predetermined number whencombustion is not established, and combustion responsive means fordeenergizing the igniter upon establishing combustion and formaintaining the fuel supply trolling said electromagnetic means toterminate operation of said cam when combustion is established, and formaintaining said fuel feeding means continuously energized thereafter,and a thermostatic switch for controlling said electromagnetic switch toefiect operation of said intermittent means to establish combustion andto stop operation of said fuel feeding means after combustion isestablished in accordance with predetermined temperature conditions.

26. In a combustion heating device, electrically operated means forfeeding fuel, and an electric igniter therefor, switch mechanism havingan electric motor driven rotatable cam. for intermittently energizingsaid fuel feeding means and igniter to initiate combustion and havingelectromagnetic means for controlling the operation of said cam, anelectromagnetic switch for energizing said electromagnetic means toinitiate the operation of said cam, means responsive to combustioncooperating with said electromagnetic switch for controlling theenergization f said electromagnetic means to terminate the op ration ofsaid cam upon establishing combustion and for maintaining said fuelfeeding means continuously energized independently of the rotatable camwhen combustion is established, and thermostatic means for controllingthe energization of said electromagnetic switch to initiate operationofsaid intermittent means under predetermined temperature conditions andto deenergize said fuel feeding means after combustion is establishedunder other predetermined tempera- .magnetic means to effectdeenergization of said ignition means and for maintaining said fuelfeeding means continuously energized upon establishment of combustion,and a temperature responsive means for energizing said secondelectromagnetic means under predetermined temperature conditions toinitiate combustion and for deenergizing said second electromagneticmeans to stop operation of said fuel feeding means after combustion isestablished under other-temperature conditions.

28. A control device for an electrically driven burner, includingelectrically operated means for intermittently energizing said burner toinitiate combustion, means for controlling energization of saidintermittent energizing means, a thermostat movable between twopositions, an electromagnetic device for operating said control meansfor said intermittent device, said electro-magnetic device beingenergized when said thermostat moves to one position, means operated bythe electro-magnetic device when said electro-magnetic device isenergized for shunting said thermostat, whereby said electro-ma gneticdevice will remain energized when-said thermostat moves to anintermediate position, and means responsive to combustion conditions forcausing deenergization of said intermittent energizing device and formaintaining said burner energized when combustion is established, saidthermostat moving to the other position to deenergize said electricallydriven burner.

29. A heating system including an electrically operated oil burner,means for intermittently energizing said oil burner to start the same,means for controlling operation of said intermittent means, a thermostatmovable between two positions, an electro-magnetic device controlledthereby for operating said controlling means for said intermittentenergizing means when said thermostat moves to one of said positions toenergize said electro-magnetic device, means operated by saidelectro-magnetic device for shunting said thermostat after saidthermostat has moved to said one position, whereby said electro-magneticdevice will remain energized when said thermostat moves to anintermediate position, means responsive to combustion for renderingsaidintermittent means ineffective with said burner energized whencombustion is established, said thermostat moving'to said other positionto stop the oil burner.

30. A heating system including an electrically operated oil burner,electrically operated means for intermittently energizing said oilburner to start operation of the same, means for controllingenergization of said intermittent means, a thermostat movable betweentwo positions, an electro-magnetic device controlled thereby foroperating said controlling means for said intermittent means tointermittently energize said oil burner when said thermostat moves toone of said positions to energize said electro-magnetic device, meansoperated by said electro-magnetic device for shunting said thermostatafter said thermostat has moved to said one position, whereby saidelectro-magnetic device will remain energized when said thermostat movesto an intermediate position, means responsive to combustion for causingdeenergization of said intermittent means when combustion is establishedwhile said burner is energized whereby said burner will remainenergized, said thermostat moving to said other position to deenergizesaid electro-magnetic means to stop the oil burner.

.31. A heating device including means for feeding fuel and an ignitertherefor, a controlling means for controlling said fuel-feeding meansand igniter to attempt to initiate combustion at predeterminedtemperature conditions, said controlling means including aconstant-speed motoroperated timing cam mechanism for repeating theignition attempts for periods of predetermined short duration atdefinite predetermined selected intervals, and means operated by saidcontrolling means for limiting the number of ignition attempts and forrendering said control system ineffective when combustion fails to takeplace during the last attempt.

32. A heating device including means for feeding fuel, an ignitertherefor, controlling means for controlling said fuel-feeding means andsaid igniter to attempt to initiate combustion, electroresponsive meansincluding a constant-speed motor-operated timing cam mechanism forrendering said controlling means effective intermittently at definitepredetermined selected intervals for periods of predetermined shortduration, and means operated by said controlling means for limiting thenumber of intermittent operations and for rendering said control systemin eifective when combustion fails to take place during the last timethat said control means is rendered effective.

33. A heating device including electrical means for feeding fuel, anigniter for said fuel-feeding means,-an electrical control forenergizing said fuel-feeding means and said igniter to initiatecombustion, an electromagnetic means and a timing cam mechanismcooperating therewith for causing repeated operation of said control atdeflnite predetermined selected intervals, means responsive tocombustionfor cooperating with said electromagnetic means formaintaining said fuelfeeding means energized when combustion isestablished independently of the operation of said timing cam mechanism,temperatureresponsive means for rendering said electro-mag netic meanseffective under predetermined temperature conditions tocauseenergization of said fuel-feeding means and igniter and forshort-circuiting said electro-magnetic means under other predeterminedtemperature conditions to cause deenergization of said fuel-feedingmeans.

34. In combination a burner having an igniter, means'for feeding fuelthereto, electrical means for controlling said fuel-feeding meanscomprising a primary thermal control means operable at a plurality ofdifferent temperature ranges, a synchronous motor connected to a powersource to be constantly energized, means operable by said motor toshiftsaid primary control means to operate at selected temperature ranges atselected times, a timing device operated by said motor and meanscontrolled by said timing device upon operation of the primary controlmeans to control said fuel-feeding means.

35. A heating system including means for feeding fuel, means forigniting said fuel, means for controlling said fuel-feeding means andsaid igniter for attempting to initiate combustion in said heater, meansincluding electro-magnetic means for operating said controlling meansintermittently at predetermined intervals for a predetermined period oftime, and means mechanically operated by said controlling means forlimiting the number of said intermittent operations and for disablingsaid controlling means when combustion fails to take place.

36. A heating device including means for feeding fuel, an ignitertherefor, of a control system comprising means for controlling saidfuel-feeding means and said igniter to initiate combustion atpredetermined temperatures, means including electro-magnetic. means forrendering said controlling means eifective for a predetermined period oftime intermittently, and

means mechanically operated by said controlling means for limiting theintermittent operation of said electromagnetic means and for disablingsaid control system when combustion fails to take place.

37. The combination with a. heating system including means for feedingfuel, ignition means therefor, of a control system therefor comprisingmeans for controlling said fuel feeding means and ignition means forattempting to initiate combustion, said means including a rotatingtiming motor for operating said controlling means to attempt to initiatecombustion at recurring definite predetermined selected intervals, andcounting mechanism associated with said controlling means and operableto disable said control system when combustion fails to take place aftera predetermined number of attempts, said mechanism thereafter requiringa manual resetting to again render said control system effective.

38. The combination with a heating system including means for feedingfuel, an igniter therefor, of a control system therefor comprising meansfor controlling said fuel feeding means and igniter to attempt toinitiate combustion, said means including a rotating timing motor forrepeating said combustion attempts for periods of predetermined shortduration at definite predetermined intervals, and counting mecha- 1

